使用 ImageMagick 裁剪具有焦点区域（脸部）的图像
我正在努力寻找带有焦点区域的调整大小、裁剪和图像的正确方法。就我而言，焦点区域是图像中检测到的脸部，我需要确保该区域在裁剪版本中可见。
我有例如给出的焦点区域。面部高度、面部宽度、面部中心x和面部中心y。这些值是原始图像尺寸的百分比。
我想做的是得到一个例如。 60x60 缩略图。正常的方法是调整大小，使图像的高度或宽度等于 60 像素，然后从中心裁剪 60x60，如下所示：
mogrify -resize 60x -gravity 'Center' -crop 60x60 image.jpg
可以采取什么方法将裁剪集中在给定区域周围？
我正在考虑一个包含多个路径的解决方案：
- 如果面部区域大于所需的缩略图，则调整图像大小足以使整个面部在 60x60 像素中可见，然后裁剪
- 如果面部区域小于所需的缩略图，然后裁剪“扩展”我的脸部区域，直到我想要的拇指可以放入该区域。然后裁剪。我想我需要确保这不会超出原始图像的范围。
有更聪明的方法吗？你能尝试制作一些示例代码吗？
谢谢！
I'm struggling to find the right approach to resize and crop and image, with a focus area. In my case the focus area is a face detected in the image, and I need to make sure that this area is visible in the cropped version.
I have focus area given by eg. face_height, face_width, face_center_x and face_center_y. These values are percentages of dimensions of the original image.
What I want to do, is getting a eg. 60x60 thumbnail. The normal approach would be to resize so either height or width of the image is equal 60px and then crop a 60x60 from center, like this:
mogrify -resize 60x -gravity 'Center' -crop 60x60 image.jpg
What approach can be taken focus my crop around a given area instead?
I'm thinking of a solution that includes several paths:
- If the face area is bigger than the wanted thumbnail, resize the image just enough to make the whole face visible in 60x60 pixels, then crop
- If the face area is smaller than the wanted thumbnail, then crop "expand" my face area until my wanted thumb can fit inside the area. Then crop. I guess I need to make sure that this doesn't exceed the bounds of the original image.
Is there a smarter approach? Can you try make some example code?
Thanks!
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我首先在脚本或程序中进行算术运算，然后将精确的坐标输入 ImageMagick。
算术步骤：
face_height、face_width、face_center_x和face_center_y到像素值。您需要矩形缩略图，因此选择最长的边并进行操作：
longest_side = max(face_height,face_width)现在您可以计算作物的左上角点：
crop_x = 面中心_x - 最长边 / 2
Crop_y = Face_center_y - Longest_side / 2
如果四个裁剪角中的任何一个超出图片尺寸，请进行调整：
crop_x和crop_y均应 >= 0crop_x + permanent_side应小于图像宽度crop_y + 最长边应小于图像高度计算完这些后，ImageMagick调用变得非常简单：
I'd first do the arithmetic in script or program, then feed exact coordinates to ImageMagick.
The arithmetic steps:
face_height,face_width,face_center_xandface_center_yto pixel values.You'll want rectangular thumbnail, so pick the longest side and operate with that:
longest_side = max(face_height, face_width)Now you can calculate top left point for your crop:
crop_x = face_center_x - longest_side / 2
crop_y = face_center_y - longest_side / 2
If any of the four crop corners fall outside your picture dimensions, adjust for that:
crop_xandcrop_yshould both be >= 0crop_x + longest_sideshould be less than image widthcrop_y + longest_sideshould be less than image heightHaving calculated these, ImageMagick call gets quite straightforward: